The present invention relates generally to a vinyl chloride resin composition, and more particularly to a vinyl chloride resin composition which possesses improved impact strength and can also provide resin products less liable to be stress-whitened upon deformation due, for example, to bending.
It has hitherto been known in the art that the impact strength of vinyl chloride resin products can be improved by blending with the polyvinyl chloride resin a graft copolymer obtained by polymerizing one or more vinyl monomers such as styrene, acrylonitrile and methyl methacrylate in the presence of a rubbery material. The vinyl chloride resin composition thus obtained has fairly satisfactory transparency and impact strength, but a formed product of the resin composition, when bent or folded, is liable to be stress-whitened around the portion at which the product is bent or folded. Especially, a formed resin product possessing high impact strength tends to be stress-whitened notably whereby the commercial value of the product is impaired.
In general, it is difficult to obtain impact strength and anti-stress-whitening property at the same time. There has been an attempt to improve both these properties by suitably coagulating a rubber latex and graft-polymerising thereonto styrene, methyl methacrylate and the like as is disclosed in Japanese Patent Pub. No. 31462/1971 and Japanese Patent Pub. No. 1584/1979, but the suitable coagulation of the latex requires a high level of technology and thus a simple method has been desired.